There are so many coins, but many of them just a copy of anothers. Why they waste their time for nothing?

"Nothing" is one of the options. Million of $ Worth of created coins is the other options, which is a very strong motivation for most of the people who create copy/paste coins. And - look at Dogecoin: by copy-pasting a coin you may even end up with a Billion $ capitalization at some point.... In this case you surely didn't waist your time.